Electric fuse



July 11, 1939. s. N. LEMMON ELECTRIC FUSE Filed Dec. 3, 1935 INVENTOR. GEORGE N. LEMMON BY HIS ATTORNEYS Patented July 11, 1939 UNITED STATES PATENT OFFICE ELEUI'BIO FUSE George N.

Lemmon, Homewood, Ala, assignor to Southern States Equipment Corporation, Birming ham, Ala a corporation of .Alabama This invention relates to circuit breakers of the expulsion tube type. More particularly it relates to spring means for ejecting or pulling out conductors from .the tube upon the occurrence of an overload. The use of springs for removing the flexible or fusible conductors from their ex-' pulsion tubes hasheretofore been known, but the spring and the associated parts have been complicated in their cooperation and-assembly and this has made installation of anew conductor within a used tube, in the fleld, a diflicult operation and in some cases it has been necessary to return the tube to the factory for insertion of a new conductor. Other springs have had the disadvantage of occupying too much space or of being situated in an inconvenient location.

This application is a. continuation in part of my copending application Serial No. 697,865, flied November -13, 1933, now Patent No. 2,090,609, issued August 17, 1937.

It is an object of my invention to provide an improved spring for removing a flexible conductor from an expulsion tube of a circuit breaker,

Another object of my invention is to provide an improved spring 'for a circuit breaker of the above'type, which has means to guide the flexible conductor as it passes through the end of the tube and means to fasten the flexible conductor to the spring.

Another object of my invention is to provide.

a spring of the above type which has means for guiding and centering the flexible conductor and for securing it to the spring. I l

Other objects and advantages of my invention will become apparent as it is described in connection with the accompanying drawing:

In-the drawing Figure 1 is a side elevation view of an expulsion tube type circuit breaker with a spring formed according to the principles of my invention. Figure 2 is a perspective view of a spring formed according to the principles of my invention.

Figure 3 is a view of one end of an expulsion tube showing my spring in operative position connected to the fusible conductor.

Figure 4 is a view similar to Figure 3 but with the spring seated in the recess of the tube terminal. I

Refen'ing to the drawing a pair of conventional pin type insulators 24 and 25 are mounted upon a" suitable support in spaced relation and have mounted upon them terminals for expulsion tube 2| of insulating material in position. The tube is provided with conventional terminals the spring 28 will Zla' and Zlb at its upper and lower ends. The upper terminal being axially recessed and the reesses being provided with internal screw threads for the reception of a screw plug 22 which presses down upon the enlarged head iii of a flexible or fusible conductor 15 which passes through the tube and hasa flexible end extending through the terminal Zlb at the lower end of thetube. Conductor l6 may he of the type which has a short portion more quickly fusible than'the rest.

In order to place the conductor l5 under tension so that any unfused portions of will be pulled out of the tube upon the occurrence of an overload I provide a helical coil spring 26 of diameter slightly less than that of the tube terminal 2"), The inner end of this spring is bent to lie diametrically across the spring axis and is provided with a loop 28 coaxial with the spring axis. This loop is of diameter slightly larger than that of the flexible conductor so that the conductor may pass therethrough and be centered and guided by the loop. This inner end of the spring presses against the end of the tube terminal 2"). The outer end of the spring 21 is coiled into a. small helical coil whose convolutions are in close proximity and whose diameter is slightly larger than that of the flexible conductor in order that the conductor may be passed through the loop. The extreme end 21' of the spring 26 is permitted to extend beyond the circumference of the small. coil 21 in order that the flexible conductors I 5 'may be guided by it as the flexible conductor is forced between adjacent convolutions of the small coil and held there frictionally. Preferably be compressed before the flexithe small coil 27 so conductor IS. The

ble conductor is fastened to that tension is applied to the extreme end of the conductor I5 is or may be in any suitable" secured to the terminal 2lb fashion such as by a screw 23.

I have found that the means I have provided. for securing the flexible conductor to the spring and for guiding the flexible conductor in its passage axially through the spring is very effective in preventing the spring from twisting itself sideways into an unworkable position. It will be observed that the guiding and securing means are part of the spring itself thus avoiding the necessity of using .additional parts to perform the essential functions of guiding and fastening.

In Figure 4 I have shown a terminal |2l which has a coaxial bore in its end for 'the reception of the spring 261. Thus it'is apparent that my invention is capable of use with expulsion tubes ametrically across the axis against sai'dfif'nd of the tube and'tending to 2 whose terminals have flat ends, or with tubes the ends of whose terminals have been bored out or formed with a recess. It will be observed howover, that in the latter kind, need of the. guide loop at the inner end of the spring is no longer imperative since the walls of the recess will guide the spring against twisting into an unworkable position. 3.

Modifications within the scope of my invention will occur to those skilled in the art and therefore I do-not limit myself to the exact form of the invention as illustrated.

I claim: v

1. In an expulsion tube type of circuit breaker having a flexible conductor extending through one end oiRthe tube and adapted to be pulled through said end upon the occurrence of an overload, a helical compression spring pressing against said end of the tube and tending to pull said conductor out of said end,.said spring having its outer end coiled into a small helical coil which is coaxial with the spring axis and has its 'conv'olutions in close proximity to one another whereby said flexible conductor may be fastened to said spring by passing between and by being held by adjacent convolutions of said small coil, said springhaving its inner end extending diof the spring and having a loop through which said conductor passes and is guided, the spring axis.

2. In an expulsion tube type of circuit breaker having a flexible conductor extending through one end of the tube and adapted to be pulled through said end upon the occurrence of an overload, a helical compression spring pressing pull-said conductor out of said end, means formed on one end of saidsp'ring to guide the flexible conductor axially as it passes through said spring, means formed on the other end of said spring for securing said conductor to said spring in the sprlngaxis:

3. In an expulsion tube type of circuit breaker, having a adapted to be pulled the occurrence of an over- 'load, a helical compression spring pressing against said end of the tube and tending to pull said conductorout et said end, means formed on opposite ends of said spring to position said conductor axiallyas it'passes through said spring and to facilitate attachmentot said conductor to said spring.

lead, a helical "compression spring pressing 60 4. In an expulsion tube type of circuit breaker having a flexible conductor extending through one end of the tube and adapted to be pulled through said end upon the occurrencepf an overagainstsaid end of the tube and said-conductor out of said. end,

tending to pull means, Iormed ne end of, said spring for attaching said conductorto-saidspring'in the spring axis 'by mere manual manipulation, and means for maintainlug the axial position of said conductor with. relation to-said sprinspendent spring member said loops being coaxial with i flexible conductorextending through 4 one end'of the tube and through said and upon fr'eely'attachable to a 5. In an expulsion tube type of circuit breaker, having a flexible conductor. extending through one end of the tube, and adapted to be pulled through said end upon the occurrence of an overload, a helical compression spring pressing against said end of the tube and tending to pull said conductor-outof said end, and means on said spring. for attaching said conductor'thereto and for guiding said conductor axially through said spring.

6. In combination, an electrical fuse link, a tubular insulating housing for said link, and a coil spring member attachable at will by mere manual manipulation to a portion of the link external to. said housing.

7. In combination, a tubular fuse housing of insulating material, a fuse link partly within and partly without said housing, and an indetensioning said link and held against said housing by said link, said spring member having a guide at one end and holding means for the link at theothenend.

8. In combination, a flexible electrical fuse link, a tubular insulation housing for said link for creating an expulsion effect on the are as said iconductor ruptures, a helical spring coaxial with the flexible conductor and attachable at will to tube.

9. In combination, a flexibleelectrical fuse link, a tubular insulation housing for said link for creating an expulsion effect on the are as said conductor ruptures, terminal members adjacent the ends of the housing, a helical spring coaxial with the flexible conductor and attachable at will to a mid-portion of the conductor by mere manual manipulation and tensioning the-portion oi the conductor within the housing but leaving untensioned a portion of the conductor exterior of the tube, and means to secure the untensioned end to'one terminal member outside the tube.

, 10. In combination, an expulsion tube fuse housing'of insulating material, a'fuse link partly within and partly without said housing, an independent coil springmember held against the end coaxial with said tube and conductor and pressingwagain'st said other end of saidtube and ten.-

.sioning said conductor, said conductor passing axially through said spring and having a loose end terminal bushing, and means .for attaching said flexible portion to said spring.

' GEORGE N. LEMMON.

flexible portion I 

